Gas-assisted electrosurgery is used to coagulate or stop blood flowing from the tissue at a surgical site. Gas-assisted electrocoagulation involves transferring arcs of electrical energy and ionized conductive pathways in a gas stream flowing to the tissue. The gas stream has the advantage of clearing blood from the tissue and allowing the arcs of electrical energy to directly enter the tissue and create a reticulum in the tissue. The reticulum forms a matrix-like structure in which the blood naturally coagulates, thereby sealing the tissue to further blood flow. Very substantial advantages result from this form of gas-assisted electrosurgery. Coagulation occurs more quickly. Coagulation is possible under conditions where coagulation was previously impossible or difficult to achieve. Less blood is lost during surgery, and the surgical procedure is completed more quickly. The high integrity of the sealed surface of the tissue, known as an eschar, almost eliminates the possibility of subsequent re-bleeding after the procedure is completed. Healing occurs more quickly because the eschar is thinner and more uniform compared to the eschar achieved by using standard, non-gas electrosurgical techniques.
Despite the numerous and significant advantages of gas-assisted electrocoagulation, certain concerns about its use have arisen. Perhaps the most significant concern is one relating to the risk of gas embolism in the patient. Gas embolism is the introduction of gas into the bloodstream of the patient. If the amount of gas in the bloodstream is significant and it accumulates in the heart, the heart can no longer pump blood. If used properly, gas-assisted electrocoagulation is safe because of its ability to rapidly coagulate and seal the tissue prior to the introduction of substantial amounts of gas. The skill of the surgeon in avoiding circumstances where gas embolism might occur, and the quality of the equipment used in the gas-assisted electrocoagulation, can influence the risks of gas embolism.
One very effective technique of avoiding gas embolism is to initiate the transfer of the arcs in the gas stream in a reliable manner and at a sufficiently-spaced distance from the tissue where the impact of the gas on the tissue does not force excessive amounts of gas into the tissue, but still causes the gas to clear blood and other fluid accumulated on the surface or stroma of the tissue. U.S. Pat. Nos. 4,781,175 and Re 34,432 describe techniques for assuring that the electrical arcs will initiate at such a distance.
Other types of gas-assisted electrocoagulation equipment use a standard, non-gas electrosurgical generator combined with a separate gas delivery device. These combination devices generally do not possess any additional arc initiation capability other than that available for initiating arcs in the still-air environment in which the standard electrosurgical generator is normally used. A still-air environment presents less difficulty in initiating arc transfer than in a flowing gas environment, because the flowing gas tends to disperse the ionized species and make it more difficult to initiate the arc transfer to the tissue. When a standard electrosurgical generator is combined with a separate gas delivery system, the gas flow may tend to "blow out" the arcs and the ionized species, making it very difficult or impossible to initiate the arc transfer to the tissue. To counteract this difficulty in initiating the arc transfer, the natural reaction is to bring the gas delivery nozzle of the applicator device into close proximity with the tissue. This slows the gas flow as a result of the inherent back pressure resulting from the close positioning. With a reduced gas flow, it is easier for the standard electrosurgical generator to initiate the arc transfer. Once the arcs are initiated, they are more easily sustained and the surgeon can withdraw the applicator to a working distance. However, a level of skill and recognition must be used by the surgeon to avoid the gas embolism risk associated with initiating the arc transfer at close working distances. Not all surgeons have this capability or even recognize the possibility of gas embolism from the incorrect use of gas-assisted electrosurgery.
The issue of positioning the gas nozzle of the applicator has recently become important because of the increasing use of gas-assisted electrosurgery in minimally invasive surgery, such as gastrointestinal, endoscopic and laparoscopic surgery. In minimally invasive gas-assisted electrosurgery, a relatively long tube-like applicator is inserted into the patient without making an open incision. A miniature camera or optical lens is also placed inside the patient for the surgeon to view the surgical site. Once the electrosurgical applicator is located in the appropriate position, the gas and electrical energy are delivered from the nozzle at the end of the tube-like applicator to achieve coagulation at the surgical site.
Gas-assisted electrosurgery is considered an advantage in minimally invasive surgery because of the very effective coagulation which can be achieved in a variety of difficult conditions and without necessitating the degree of control and precision in placement required to achieve good coagulation with standard, non-gas electrosurgery under similar conditions. Placement is particularly important because it is very difficult to visualize the surgical site and the position of the applicator relative to the tissue with the monoscopic view available to the surgeon through the miniature camera or optical lens. In other words, the surgeon does not have the benefit of depth perception when viewing the surgical site monoscopically, making positioning very difficult. Indeed, it is not uncommon for the surgeon to fail to realize that the nozzle of the applicator is either in contact with or buried into the tissue. Such conditions are highly conducive to a risk of gas embolism because the gas may directly enter the tissue. In conditions where the nozzle is adequately spaced from the tissue, the more uniform coagulation effects available from gas-assisted electrosurgery compensate for the lack of position recognition available to the surgeon.
It is with respect to these and other considerations, that the present invention has evolved.